Derivative Instruments Derivatives 1 - Notional and FV Position (Details) (USD $)	Mar. 31, 2014		Dec. 31, 2013
Asset Derivatives [Abstract]
Notional amount	$ 244,961,000,000		$ 245,573,000,000
Derivatives asset, estimated fair value	836,000,000		2,073,000,000
Netting adjustment	(8,422,000,000)	[1]	(8,422,000,000)	[1]
Derivative Liabilities [Abstract]
Notional amount	378,875,000,000		380,094,000,000
Derivative liability, estimated fair value	(209,000,000)		(1,469,000,000)
Netting adjustment	10,042,000,000	[1]
Table Footnote [Abstract]
Cash collateral posted for derivative instruments	2,800,000,000		2,000,000,000
Cash collateral received for derivative instruments	1,200,000,000		1,000,000,000
Risk Management Derivatives [Member]
Asset Derivatives [Abstract]
Notional amount	203,393,000,000		205,736,000,000
Derivatives asset, estimated fair value	8,226,000,000		9,444,000,000
Accrued interest receivable, estimated fair value	927,000,000		786,000,000
Netting adjustment	(8,422,000,000)	[2]	(8,422,000,000)	[2]
Total net risk management derivatives	731,000,000		1,808,000,000
Derivative Liabilities [Abstract]
Notional amount	335,539,000,000		346,994,000,000
Derivative liability, estimated fair value	(8,990,000,000)		(9,695,000,000)
Accrued interest payable, estimated fair value	(1,143,000,000)		(930,000,000)
Netting adjustment	10,042,000,000	[2]	9,370,000,000	[2]
Total net risk management derivatives	(91,000,000)		(1,255,000,000)
Mortgage commitment derivatives [Member]
Asset Derivatives [Abstract]
Notional amount	41,568,000,000		39,837,000,000
Derivatives asset, estimated fair value	105,000,000		265,000,000
Netting adjustment	0	[1]	0	[1]
Derivative Liabilities [Abstract]
Notional amount	43,336,000,000		33,100,000,000
Derivative liability, estimated fair value	(118,000,000)		(214,000,000)
Netting adjustment	0	[1]	0	[1]
Pay-fixed Swap [Member] | Risk Management Derivatives [Member]
Asset Derivatives [Abstract]
Notional amount	68,984,000,000		68,637,000,000
Derivatives asset, estimated fair value	3,746,000,000		5,378,000,000
Derivative Liabilities [Abstract]
Notional amount	94,488,000,000		93,428,000,000
Derivative liability, estimated fair value	(5,083,000,000)		(4,759,000,000)
Receive-fixed Swap [Member] | Risk Management Derivatives [Member]
Asset Derivatives [Abstract]
Notional amount	67,408,000,000		67,527,000,000
Derivatives asset, estimated fair value	3,842,000,000		3,320,000,000
Derivative Liabilities [Abstract]
Notional amount	144,897,000,000		156,250,000,000
Derivative liability, estimated fair value	(2,833,000,000)		(3,813,000,000)
Basis Swap [Member] | Risk Management Derivatives [Member]
Asset Derivatives [Abstract]
Notional amount	23,414,000,000		27,014,000,000
Derivatives asset, estimated fair value	70,000,000		36,000,000
Derivative Liabilities [Abstract]
Notional amount	600,000,000		600,000,000
Derivative liability, estimated fair value	0		0
Foreign Currency Swap [Member] | Risk Management Derivatives [Member]
Asset Derivatives [Abstract]
Notional amount	368,000,000		389,000,000
Derivatives asset, estimated fair value	126,000,000		120,000,000
Derivative Liabilities [Abstract]
Notional amount	492,000,000		653,000,000
Derivative liability, estimated fair value	(26,000,000)		(38,000,000)
Pay-fixed Swaption [Member] | Risk Management Derivatives [Member]
Asset Derivatives [Abstract]
Notional amount	34,450,000,000		33,400,000,000
Derivatives asset, estimated fair value	259,000,000		445,000,000
Derivative Liabilities [Abstract]
Notional amount	46,025,000,000		48,025,000,000
Derivative liability, estimated fair value	(475,000,000)		(600,000,000)
Receive-fixed Swaption [Member] | Risk Management Derivatives [Member]
Asset Derivatives [Abstract]
Notional amount	8,000,000,000		8,000,000,000
Derivatives asset, estimated fair value	154,000,000		117,000,000
Derivative Liabilities [Abstract]
Notional amount	49,025,000,000		48,025,000,000
Derivative liability, estimated fair value	(572,000,000)		(484,000,000)
Other [Member] | Risk Management Derivatives [Member]
Asset Derivatives [Abstract]
Notional amount	769,000,000	[3]	769,000,000	[3]
Derivatives asset, estimated fair value	29,000,000	[3]	28,000,000	[3]
Derivative Liabilities [Abstract]
Notional amount	12,000,000	[3]	13,000,000	[3]
Derivative liability, estimated fair value	(1,000,000)	[3]	(1,000,000)	[3]
Mortgage Commitments to Purchase Whole Loans [Member] | Mortgage commitment derivatives [Member]
Asset Derivatives [Abstract]
Notional amount	2,205,000,000		1,138,000,000
Derivatives asset, estimated fair value	3,000,000		1,000,000
Derivative Liabilities [Abstract]
Notional amount	3,665,000,000		4,353,000,000
Derivative liability, estimated fair value	(11,000,000)		(31,000,000)
Forward Contracts to Purchase Mortgage-related Securities [Member] | Mortgage commitment derivatives [Member]
Asset Derivatives [Abstract]
Notional amount	11,553,000,000		3,276,000,000
Derivatives asset, estimated fair value	24,000,000		4,000,000
Derivative Liabilities [Abstract]
Notional amount	21,370,000,000		20,861,000,000
Derivative liability, estimated fair value	(62,000,000)		(168,000,000)
Forward Contracts to Sell Mortgage-related Securities [Member] | Mortgage commitment derivatives [Member]
Asset Derivatives [Abstract]
Notional amount	27,810,000,000		35,423,000,000
Derivatives asset, estimated fair value	78,000,000		260,000,000
Derivative Liabilities [Abstract]
Notional amount	18,301,000,000		7,886,000,000
Derivative liability, estimated fair value	$ (45,000,000)		$ (15,000,000)

[1] Represents the effect of the right to offset under legally enforceable master netting arrangements to settle with the same counterparty on a net basis, including cash collateral posted and received and accrued interest.

[2] The netting adjustment for our risk management derivatives transactions represents the effect of the legal right to offset under legally enforceable master netting arrangements to settle with the same counterparty on a net basis, including cash collateral posted and received. Cash collateral posted was $2.8 billion and $2.0 billion as of March 31, 2014 and December 31, 2013, respectively. Cash collateral received was $1.2 billion and $1.0 billion as of March 31, 2014 and December 31, 2013, respectively.

[3] Includes interest rate caps, futures, swap credit enhancements and mortgage insurance contracts that we account for as derivatives. The mortgage insurance contracts have payment provisions that are not based on a notional amount.